Tumour thickness, diameter, area or volume? The prognostic significance of conventional versus digital image analysis-based size estimation methods in uveal melanoma

Abstract

Purpose: The aim of this study was to compare conventional and novel size estimation methods' ability to predict survival in uveal melanoma (UM).

Methods: The study was designed as a retrospective consecutive chart review of patients with UM, enucleated between the years 1984 and 1993. Area and volume were estimated based on the largest histopathological cross-section, the second centroid theorem of Pappus and digital image analysis, correlated to overall and relative survival.

Results: Of 168 patients analysed, 20 (12%) of tumours were categorized as T1, 47 (28%) as T2, 67 (40%) as T3 and 19 (11%) as T4 (15 N/a). A total of 91 tumours with complete survival and measurement data were included and recategorized into small, medium and large volume groups. Increased separation of overall survival was seen compared with current American Joint Committee on Cancer T categories. Difference between the large and small volume groups was 8.6 years (p = 0.001), compared to a difference of 5.6 years (p = 0.091) between T1 and T4. Hazard ratio for all-cause mortality in the large versus small volume group was 2.6 compared to 1.9 for T4 versus T1. Relative survival rates for small, medium and large volumes were 62, 44 and 31% at 10 years, versus 50, 45, 56 and 0% for T1, T2, T3 and T4.

Conclusion: This study provides evidence that a novel UM volume estimation method might offer a practical and cost-efficient alternative to improve the prognostic value intrinsic to a tumour's size.

Keywords: classification; digital image analysis; size; uveal melanoma; volume.